Threading tool



Patented July 1927.

UNITED STATES PATENT OFFICE.

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This invention relates to taps-'and other threading tools and has for its object to materially increase their useful life so that a much greater wear may occur before the threads cut'thereby will refuse a master gage.

For the purpose of lllustratlon, this 1nvention will be more fully described vin connection with the production of United States standard threads,vthough it should be recognized that it,is applicable togan form of threads, and with vreference to t e accome panying draWings-rn whichvscrew engaging it.

Figure 1 is a through a portion o p form of nut with av basic gmentary crosssection a basicor theoretical or theoretical Figure 2 is asimilar view` of the `nut illustrating the contour cut after a tool of theoretically correct contour has been in use for different periods of time.

Figure 3 is a similar view illustrating one method of prolonging the life of the cutting tool and showing the wear thereon. v

Figure 4 is va similar view illustrating a modied construction according to thisinvention. Y

Figures 5 and 6 are` detail sections illustrat-ing slightly different constructions.

Referring to Figure 1 it will be seen that the nut 1 has threads formed therein having their Hanks 2 inclined to each kother at an angle of and that the to and bottom of the threads are flattened o as at 3 to a width equal to 1/8 of the pitch.- The screw` 5 engaging with `the nut is formed complemental to the nut. The dotted line :zz-w represents the nominal or basic major diameter of the thread, the line y-y the basic pitch diameter, and the line z`-z the basic minor diameter of theA thread. If in cutting the threads in the nut a tool having its end shaped exactly in accordance with the -desired contour as shown at 10 in Figure 2 is employed, after Ka-few, minutes of cutting the corners adjacent to its apex, as at 11, become rounded over as shown at 12 in Figure 2, this rounding over increasing as the tool continues in use' until it becomes quite marked as shown at 13 in Figure 2. It is only a short time before this rounding over is suicient to cause the nut to reject a standard screw or gage having the apex of its threads of the correct con- Stein; e

or truncated In order to obviate this diiculty of the wear of the tool soon rendering its cutting insuicient to receive the master gage, it has been custom to, prolon tool beyond e majoriameter fai-, as shown in Figure 3, so that the rounding of the apex due to wear on the tool may be quite` considerable, as shown' progressively at 15rand 16 in Figure 3, before it affects the cutting of any ortion of the thread whichis engaged by t e thread of the stand-,A ard gage. After a time, however, it does be-f,` come rounded to such an extent that thei thread cut thereby will reject the standard ge, According to the present invention, the apex of the ltoolpis prolonged beyond the major diameter but instea 'approximately 30".. The wear on this ex-` tension may thus be much more extensive of being pro.

longed in line with its flanks it is prolonged ,along lines making a more acute angle'with each other than these flanks as shown in Fig-y the'apex of the than on the extension shown in Figure 3 ,by Y the dotted line A21, before it has any eif'ect on that portion of the thread which is en-y the standard gage. By forming of the extension moreacute than that of the flanks of the thread to be made,

the tool end is much widened andtherefore much more tool material will have' to be worn of before the wear extends to a point vbelow the basic lma'or diameter,'causing the gzge traveling'in t e path made thereby to rejected. If desired, the sides of this extension could be made substantially parallel as shown at 25 in Figure 4, in which case rmissible wear would extend to the dv line 26. If desired, the modified outline v'of this extension could be carried to a point slightly below the basic major diameter as shown in Figure 6 at 30, thus further increasing the tool stock which 4might be worn away without causing a standard screw or gage to be'rejected, as shown by dotted line 29. The threads at the major diameter would then at first be cut somewhat larger thanV the tops of the threads of the standard screw or gage, but if this is not done to too at an extent, the usefulness or reliagre bility of the threaded hole will not be af.

fected to any practicable extent. If desired also themodication of the apex of the tool might be entirely above the basic major diameter as shown at 31 in Figure 5, in which case permissible Wear would extend to theY dotted line 32. The effect of the additional 'material in each of the constructions shown is further intensied by the fact that the pitch diameter of the tap or internal threading tool is not made basic but slightly above basicwithin the necessary tolerance limits to allow for Wear on the flanks as Well as lon the points.

While the tool has been shown in connection with the production of the threads of a nut, of course it could be employed similarly to the production of the threads of a screw, the modified extension of the tool end then extending below the minor diameter of the thread of the engaging nut rather than above the major basic diameter.y For the purposes of this application, therefore, the term extreme diameter is intended to cover both the basic major diameter in the case of a nut and in the case of a screw' the minor diameter' of its engaging nut, whether or not this is the minor basic diameter. In each instance, however, the portion of the tool modified in shape substantially, i. e. beyond Vthe usual tolerance limits, from that of a section of the member which is to engage in the path cut, is at the apex only of the tool.

Having thus described certain embodiments of this invention, it should be evident to those skilled in the art that various changes and modifications may be made therein without departing from its` spirit or scope as dened by the appended claims.

l claim:

l. A thread cutting tool having` its apexv formed at a more acute angle than'the Hanks of adjacent threads to be cut.

2. A thread cutting tool having its apex formed at a more acute angle than the flanks of adjacent threads to be cut and extending beyond the extreme diameter of said thread.

3. A thread cutting tool having a portion at its apex only substantially Wider than a corresponding portion of the thread engage able in the path cut by said tool.

4. A thread cutting tool having a portion at its apex only ,substantially wider and longer than a correspondingportion of the thriad engageable in the path cut by said too 5. A thread cutting tool having a portion at its apex only substantially Wider and longer than a corresponding portion of thel thread engageable in the path cut by said tool, part of said -wider portion lying with? in the extreme diameters of said thread.

1n testimony whereof I have axed my signature. I

s RALPH E. FLANDERS. 

